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Its when you lose those restrictions that the HV pump comes into play. More bearing clearance, full time top end oiling, pressurized roller lifters, pushrod oiling, full roller rockers, etc.. The downside is if you're going o move more volume you damn well better have the volume to move. A HV pump will drain a stock big block or hemi/six pack pan in the quarter mile. Anything less than a seven quart pan and you're just beggin' for trouble. [/quote]
I used a Melling hi volume oil pump with a 1970/71 Mopar Hemi/6 pack 6 quart oil pan with Indy SR heads oiling the rockers full time with .0034 rod bearing clearances, .0042+ main bearing clearances in a 400 block with solid roller lifters with no lifter bushings, it would cross the 1/4 mile finish line at or close to 7000 RPM and not have any oil pressure problems until I let it get down one quart low down to the add mark at the races It would start to loose oil pressure after I let off about 100 to 200 feet past the finish line, if I tap the gas a little bit it would get the oil pressure back sooner than let it slow down in gear all the way to the turn off
It wouldn't loose oil pressure ever with the oil pan full up near the full mark with 6 quarts in those pans
I do build and use crankshaft scrapers on all my motors now